Millions were uprooted and sent to the countryside for re-education and hard labor. Millions more were persecuted, publicly humiliated, tortured, executed.

All of which is why, when Li first made this comparison — at a lunch with American journalists sponsored by the Asia Society — I laughed. Li is known as a sort of rhetorical bomb-thrower, an expert defender of the Communist regime, and this seemed like just another one of his explosive remarks.

And yet I haven't been able to get the comment out of my head. In the weeks since I've returned stateside, Li's seemingly far-fetched analogy has begun to feel … a little too near-fetched.

Li said he saw several parallels between the violence and chaos in China decades ago and the animosity coursing through the United States today. In both cases, the countries turned inward, focusing more on defining the soul of their nations than on issues beyond their borders.

He said that both countries were also "torn apart by ideological struggles," with kinships, friendships and business relationships being severed by political differences.

"Virtually all types of institutions, be it political, educational, or business, are exhausting their internal energy in dealing with contentious, and seemingly irreconcilable, differences in basic identities and values — what it means to be American," he said in a subsequent email exchange. "In such an environment, identity trumps reason, ideology overwhelms politics, and moral convictions replace intellectual discourse."

Li also pointed to the "big-character posters" — large, hand-painted propaganda slogans and calls to action — used during the Cultural Revolution to denounce purported enemies of the state and call for class struggle against them.

These find a contemporary counterpart in the hashtags and public pilings-on in social media, which also frequently leverages paranoia and mob rule. Today's big (280) character posters — whether crafted by public figures, trolls, political groups or us laobaixing (commoners) — often take the form of calls for resignations or collective harassment, threats of violence and attacks on adversaries as "the enemy of the American People."

Li didn't mention these other similarities, but in both periods: Higher education is demonized. National symbols and cultural artifacts once seen as unifying, such as the Statue of Liberty and the American flag, become politicized. Specific words and ideas are stricken or banned from government communiques.

Both Mao's decade-long tumult and today's Cultural Revolution with American characteristics also feature cults of personality for the national leader, who thrives in the surrounding chaos. Each also gives his blessing, sometimes explicitly, for vigilantes to attack ideological opponents on his behalf.

But the most troubling parallel is the call for purges.

Then, Mao and his allies led purges of political and military ranks, allegedly for seditious or just insufficiently loyal behavior. Today, White House officials, right-wing media hosts and federal lawmakers have called for a "cleansing" of the nation's top law-enforcement and intelligence agencies, because the "deep state" is conspiring against the president.

"We are at risk of a coup d'etat in this country if we allow an unaccountable person with no oversight to undermine the duly elected president of the United States," Rep. Matt Gaetz, R-Fla., said on the House floor in November, as he called for special counsel Robert S. Mueller III to resign or be fired. He repeated this demand on TV last week.

Also last week, Rep. Francis Rooney, R-Fla., called for a "purge" of both the Justice Department and FBI to remove the influence of the "deep state."

The more you look around, the more parallels appear. It's almost like — stick with me here! — authoritarian, anti-intellectual, expulsionist tendencies are not confined to halfway around the world, half a century ago. Political tribalism can be fed and exploited for personal gain in any society, even our shining city on a hill.

What differentiates the (fully cataclysmic) China then from the (only relatively chaotic) United States now is, among other things, our political institutions. Our system of checks and balances. And perhaps a few statesmen willing to keep those institutions, checks and balances in place — occasionally turning their backs on their own political tribe.